1. Field of the Invention
The present invention relates to a reciprocating compressor, and more particularly, to a motor fixing structure of a reciprocating compressor capable of simplifying a motor assembly and preventing an assembly dimension variation after the motor assembly.
2. Description of the Conventional Art
Generally, a reciprocating compressor is an apparatus for sucking and compressing refrigerant gas in accordance with a piston reciprocates in a cylinder. The reciprocating compressor is largely divided into two methods by a driving mechanism. One is a method that a rotary motion of a motor is converted into a linear reciprocation motion thus to be transmitted to a piston, and the other is a method that a linear reciprocation motion of a motor is directly transmitted to a piston.
FIG. 1 is a view showing one embodiment of a reciprocating compressor in which a linear reciprocation motion of a motor is directly transmitted to a piston. As shown, the reciprocating compressor comprises a casing 10 to which a gas suction pipe 1 and a gas discharge pipe 2 are coupled, a front frame 20 and a middle frame 30 installed in the casing 10 with a certain interval by being elastically supported, a driving motor 40 installed between the front frame 20 and the middle frame 30 for generating a driving force, a cylinder 50 inserted into the front frame 20, a piston 60 for receiving a driving force of the driving motor 40 and thus linearly reciprocating in the cylinder 50, a rear frame 70 for covering the piston 60, a resonance spring 80 for inducing resonance by elastically supporting the piston 60, and a valve assembly 90 for opening and closing a gas channel in order to suck and compress gas into the cylinder 50 according to a linear reciprocation of the piston 60.
The driving motor 40 includes an outer stator 41 mounted between the front frame 20 and the middle frame 30, an inner stator 42 inserted into the outer stator 41 with a certain interval and mounted at the front frame 20, a winding coil 43 coupled to the outer stator 41, and a mover linear-movably inserted between the outer stator 41 and the inner stator 42. The mover 44 is composed of a holder 45 of a cylindrical shape and a plurality of magnets 46 coupled to the holder 45, and the holder is connected to the piston 60.
An unexplained reference number 100 denotes a coupling bolt, 101 denotes a nut, 102 denotes a discharge cover, and 103 denote a valve spring.
Operation of the reciprocating compressor will be explained as follows.
First, when an electric power source is applied to the driving motor 40, a flux is formed at the outer stator 41 and the inner stator 42 by an electric current applied to the winding coil 42 of the driving motor 40. By an interaction between said flux and a flux formed by the mover 44, the mover 44 linearly reciprocates and thereby the piston 60 linearly reciprocates in the cylinder 50. By a pressure difference inside of the cylinder 50 by the linear reciprocation of the piston 60, the valve assembly 90 opens and closes a gas channel thus to suck gas into the cylinder 50, compress, and discharge. Said processes are repeated and thereby gas is continuously compressed.
A performance and a reliability of the reciprocating compressor are influenced by an air gap between the outer stator 41 and the inner stator 42 into which the mover 44 of the driving motor is inserted. Accordingly, at the time of assembling the reciprocating compressor, it is important to assemble the driving motor 40 in a condition that the air gap of the driving motor 40 can be maintained as it is. Also, it is important to maintain the air gap constantly even at the time of driving the reciprocating compressor.
In the conventional motor fixing structure of the reciprocating compressor, as shown in FIGS. 2 and 3, the inner stator 42 is fixedly coupled to a cylindrical body 21 of the front frame, and one side surface of the outer stator 41 is in contact with an inner side surface of a plate portion 22 of the front frame extending and formed at one side of the cylindrical body 21 with a certain area. Also, one side surface of the middle frame 30 having a predetermined thickness and an area is in contact with the other side surface of the outer stator 41. A plurality of coupling bolts 100 are inserted into the front frame 20 and the middle frame 30 with a certain interval, and the nuts 101 are coupled to the coupling bolts 100 thus to couple the front frame 20 and the middle frame 30 to each other. By the coupling between the front frame 20 and the middle frame 30, the outer stator 41 is fixedly coupled.
The outer stator 41 is formed in accordance with thin plates L1 of a predetermined shape are radially stacked as a cylindrical shape. At this time, the thin plates L1 are radially stacked on the winding coil 43 of a ring shape. The outer stator 41 and the winding coil 43 positioned in the outer stator 41 are molded with a plastic resin material for insulation and shape maintenance.
The inner stator 42 is formed as a cylindrical shape having a certain length in accordance with thin plates L2 of a quadrangular shape are radially stacked at an outer circumferential surface of the cylindrical body 21 of the front frame.
The construction components are assembled by using a jig in order to constantly maintain an interval between an inner circumferential surface of the outer stator 41 and an outer circumferential surface of the inner stator 42 and an interval between the inner/outer circumferential surfaces and the mover 44 inserted therebetween.
In the conventional motor fixing structure, the outer stator 41 is fixed by coupling the plurality of coupling bolts 100 and the nuts 101 in a state that the front frame 20 and the middle frame 30 are respectively in contact with both side surfaces of the outer stator 41, thereby simplifying the structure, reducing an assembly dimension modification for the air gap maintenance, and thus enabling a great quantity of production. However, a fixing of the driving motor 40 becomes inferior by a vibration generated when the compressor is operated, that is, when gas is sucked and compressed while the piston 60 linearly reciprocates in the cylinder 50, so that the air gap is not constantly maintained. Additionally, when the motor is operated for a long time, a dimension of the outer stator 41 is diminished by a molding of the outer stator 41, thereby increasing a dimension variance of the air gap. According to this, the mover 44 linearly reciprocating between the outer stator 41 and the inner stator 42 is in contact with the outer stator 41 and the inner stator 42, thereby causing abrasion and damage of the components and thus degrading a reliability of a product.